Temperature control device



Nov. 17, 1936. w. J. ETTINGER TEMPERATURE CONTROL DEVICE Filed May 22, 1934 J bu Fags.

V invent-or.

Wallace .1. Etti g b 77 4 ,7 M11 His Attorneg.

Patented Nov. 17, 1936 PATENT OFFICE 2,061,418 TEMPERATURE ooN'rnoL DEVI-CE Wallace]. Ettinger. Chicago, Ill., assignor to Edison General Electric Appliance Company, Chicago, 111., a corporation of New York Application May 22, 1934, Serial No. 726,891 4 Claims. (01. 200-139) This invention relates to temperature control devices, more particularly to devices for control ling an. electric circuit in accordance with temperature changes, and it has for its object the 5 provision of an improved device of this character.

In general this invention relates to temperature responsive devices such as described and claimed in the United States reissue patent to lo A. Lewerenz No. 16,654, dated June 14, 1927, and

in the United States patent to A. H. Simmons No. 1,743,073, dated January 7, 1930 and more specifically relates to improvements in one form of the temperature control device described and claimed in the copending application of Francis H. McCormick, Serial No. 575,593, filed November 17, 1931, and assigned to the same assignee as this invention. and which is an improvement of certain features of the Simmons patent. These temperature control devices comprise a bimetallic theremostat bar fixed at one end and having its other end free to move in response to changes in temperature. These movements of the bimetallic bar are utilized to operate a suitable, control member, such as a switch arm. .Bearing on the movable end of the bimetallic bar is an elastic member arranged to, cause the bar to move quickly from one position to another and thereby give the switch a snap action in opening and closing the circuit which it controls. This invention is particularly applicable to a thermostatic device such as shown in the Mc- C'ormick application wherein two separate sets of switch contacts are controlled by the switch 35 arm, and contemplates the provision of improved operable connection means between the control arm and the bimetallic thermostat bar, whereby a rugged; reliable and efficient device is obtained. -In accordance with this invention, the elastic 40 member which bears on the movable end of the g bimetallic thermostat bar has a substantially U- shape. A comparatively. rigid. andmechanically strong switch arm is mounted longitudinally on the base of the U-shaped spring member and has a loose connection with this member so that it can rotate'on the base on axes arranged both transversely and longitudinally of the base.

The loose connection means between the arm and the spring provides for limited freedom of movement of these -members relative to each other. Preferably, suitable elastic means will be provided for biasing the control arm toward the base of the spring so that when the arm is in either of its controlling positions to close the corresponding switch contacts, the arm will be urged against the contacts by an elastic force. By reason of this elastic, force applying means and the loose connection between the arm and,the.U- shaped spring, the bimetallic bar when moving between its controlling positions acquires consid- 5 erable velocity before the contact arin is actuated to open the one set of switch contacts and to close the other.

For a more complete understanding of this in-' vention, reference should be had to the accompany-ing drawing in which Fignl is a vertical central sectional view of a temperature control device embodying this invention; Fig. 2 is a plan view of the temperature control device of Fig. 1 but having a certain member removed so as to illustratecertain details of construction; and Fig. 3 is a vertical central sectional view of a temperature control device illustrating a modification of my invention. 0

Referring more particularly to. Figs. 1 and 2, this invention has been shown in one form as applied to a temperature responsive device intended to be used to control rather large currents, such' as those encountered in domestic hot water heating systems, but it:is to be understood that it is applicable tothermostats that are used in systems where the currents are relatively small and also insystems wherein the currents handled are considerably larger than those encountered in domestic hot water systems. As shown, the temperature control device comprises a base or supporting member ID formed from a suitable metallic material, such as aluminum. The base I0 is provided with integral end and side walls II and I2 respectively rising vertically therefrom so as to define a substantially rectangular casing.

A suitable temperature responsive member [3,

- shown as a bimetallic thermostat blade or bar is mounted upon the support l0.-

blade is made of two strips of metal having dissimilar temperature coefllcients of expansion, such .as brass and invar, the strips being securely brazed 0r welded together likewise. The bar 13 is rigidly secured at one end to the support H! by means of clamping screws l4 passed through apertures provided for them in the bar and received in threaded apertures provided for them in the base Hi. It will be observed ,that the other end of the bimetallic bar is free to move laterally in response to'changes in temperature.

An adjusting screw I5 is provided near the fixed end of the bar l3.' This screw is passed justing screw l5, as shown, has a shoulder 6 that bears against a suitable thrust plate II which extends transversely of the casing above the bimetallic bar l3. The thrust plate H extends substantially the full width of the base In and has its opposite end portions turned downwardly at right angles to the body portion to form depending portions Ila which are retained against lateral movement by means of abutments 8 on their right-hand side, as viewed in Fig. l, and by means of bosses on their other side. The plate H is provided on its lower surface with bearings 2| arranged on opposite sides of the adjusting screw l5 and resting on the upper surface of the bimetallic bar |3. Only one of these hearings 2| has been shown.

It will be understood that the bimetallic bar l3, by reason of its elasticity and the initial curvature given the blade, forces the thrust plate upwardly against the abutment l6 provided on the adjusting screw I5, and that'the thrust plate may be moved downwardly by means of the adjusting screw against the elastic force of the bimetallic bar to change its position relative to the base l0.

The movable end of the bimetallic bar is provided with a knife edge bearing 22. Between this hearing and a bearing 23 secured in the adjacent end wall II of the casing is interposed an inverted substantially U-shaped resilient member or spring 24. As shown, one arm of this spring has a bearing seat 25 which receives the knife edge bearing 22 on the bar I3, while its other arm has a bearing seat 26 which receives the bearing 23. Thebearing seat 25 corresponds to the knife-edge bearing 22. The bearing 23 rather than being formed as aknife-edge has a pivotal or substantially conical form, as clearly shown in Fig. 1. The seat 26 in the spring 24 is shaped to conform to this pivot. The spring 24 preferably will be formed of a suitable moisture resistant material, such asberyllium bronze.

The bearing pivot 23, as shown, is mounted upon the end of a screw 21 which is threaded in the adjacent end wall ll of the casing. The

-screw 21 is provided with a slotted end 21a whereby the position of the screw and hence that of the pivot bearing 23 can be changed with an ordinary screw driver or similar instrument. The screw 21 is secured in its adjusted position by means of a lock nut 28. It will be observed in view of the foregoing construction that the position of the bearing 23 can be readily adjusted relatively to the bearing 22 on the bimetallic bar so as to change the tension in the spring member 24. The screw 21 and its lock nut 28 are formed of steel, rendered corrosion resistant by cadmium plating.

As 'pointed out in detail in the above-mentioned Simmons patent, the function of the U- shaped spring member 24 is to move the thermo stat bar- |3 quickly between its controlling positions. And further, that adjustment of the screw I5 changes the temperature setting of the de vice, while the range between the maximum and minimum temperatures at which the device operates is controlled by adjusting the position of the pivot 23 to vary the span of the U-shaped spring 24, that is, to vary its tension.

A substantially rigid and mechanically strong switcharm 30 is secured to the base of the U- shaped spring member 24, as shown in Fig. '1.

The arm 38 is secured to the base of the spring Y so that it has pivotal motion relative to the base on a pair of axes arranged transversely of the sides with locking abutments 32 which engage the underside of the spring to prevent withdrawal of the spring arm. However, the portions of the lugs between the switch arm and the abut ments, as shown, have a suiiicient length to provvide for relative limited freedom of movement of the switch arm vertically relative to the base of the spring. The switch arm can be assembled with the spring by projecting the lugs with their locking portions 32 through elongated parts of the slots 3|a provided in the spring and shown at the upper sides of the slots in Fig. 2, and then shifting the arm transversely to bring the lockingabutments 32 of the lugs 3| under the abutments 34 provided in the spring.

The switch arm is biased toward the base of the spring by means of a compression spring 35 which is mounted upon a pin or shaft 36 that is passed through" apertures provided for it in the switch arm and the base of the springmidway between its ends, as clearly shown in Fig. 1. The pin has heads 31 on its opposite ends, the upper of which bears on the upper surface of the arm 30, while thelower serves as an abutment for the lower end ofv thev spring. The upper end of the spring, as shown, bears against the under side of the U-shaped spring member 24. Suitable knife-edge bearings 38 are provided on the upper surface of the switch arm arranged transversely of the arm on opposite sides of the aperture in the arm provided for the pin and on an axis passing substantially through the center of the pin so as to' bear against the under surface of the adjacent head 31 of the pin.

The switch arm 30 is also provided with a pair of bearings 40 on the under side of the arm arranged to bear on the upper surface of the U- shaped spring member. These bearings also are arranged on opposite sides of the pin 35, and in this case are arranged on an axis arranged longitudinally of the switch arm passing substantially through the center of the pin.

The bearings 38 on the upper surface of the switch arm and the bearings 40 on its under surface are formed in any suitable manner, but preferably will be made by pressing them out from the material of the arm.

In view of the foregoing arrangement, it will be observed that the switch arm has pivotal movement on the base of the spring 24 about a pair of transverse axes which pass through the bearings 48. In other words, the arm can rock upon the base of the spring member on axes passing through both of these bearings. v

The arm also can be pivoted or rotated on these bearings on an axis arranged longitudinally of the base of the spring.

The switch arm 38 carries on its free end a pair of bridging contacts 4| and 42 which are arranged to engage sets of fixed contacts 43 and 44 respectively arranged in pairs. The bridging contacts 4| and 42 are separated from theswitch arm 30 by layers 45and 46 respectively of a suitable electrically insulating material, such as mica. The two bridging contacts and the sheets of mica are secured to the switch arm by means of a rivet 7 .tion, as shown in Fig. 1.

turn are secured to the insulating member 41 by means of rivets 5|.

vided with suitable binding screws 52 with which These terminals are proelectrical connections are made. Likewise, the fixed contacts 44 are secured to terminals 53 whichare secured to the insulating member 48 by means of rivets 54. Suitable binding screws 55 are secured to the terminals 53. The terminals and binding screws preferably will be formed of brass.

The lower insulating member 48 rests upon the bosses 20 and the guides l8, which as previously pointed out, are provided in the side walls l2 at the sides of the thrust plate 11. The upper insulating member 41 rests upon suitable upright walls 44b provided on the side portions of the lower member 48. The two insulating members are secured together and to the base by means of screws 58 which pass through apertures provided for them in the insulating members and received in threaded engagement with the bosses 20. The screws 58 are rendered moisture resistant by means of cadmium plating. The lower insulating member 48 is provided with an upright cylindrical sleeve 59 (Fig. 2) extending from its upper surface and surrounding the adjusting rod or. screw I5, while the upper member 41 is provided with a recess 41a that receives this cylindrical member.

The electrical connections are made with the binding posts 52 and 55 by directing the leads or conductors through an aperture 60 provided in one of the end walls ll, preferably, in the end wall adjacent the binding screws, as shown in Fig. 1. The aperture 60 is lined with an eyelet Bllafwhich preferably will be formed of brass,

A. suitable cover member 6| is secured to "the casing by any suitable means, such as by means of screws 62 which are received in threaded engagement by bosses 63 arranged in the corner portions of the casing.

The cover member BI is provided with an aperiture 64 for receiving the cylindrical sleeve 59 of the rod l5 can be effected conveniently. Secured to the upper end of the adjusting screw I5 is an index or pointer 66 which cooperates with a suitable temperature scale (not shown) arranged on the upper surface of the cover 6I so as to assist in making the temperature settings. The insulating sleeve" 59 is provided at its upper end with an arcuate wall 59a, the ends of which act as stops cause it prevents the atten'dant'from moving the adjustment beyond this normal range thereby obviating adjustments of the device which would destroy its calibration.

As shown, the cover BI is lined with an electrically insulating sheet 61 which may be made of a suitable phenol condensation product.

The base member ID is provided with a plurality of apertures 68 through which suitable screw fastening means (not shown) may be passed to secure the base in thermal relation with the body whose temperature is to be controlled.

' Thus, for example, the base may be secured to the side walls of a water heater storage tank, whereby the bimetallic bar .I3 is caused to respond to the temperature of the water. It will be observed that the bottom wall of the casing is relatively thin so that when the casing is thus applied to the side walls of a tank or similar device, the temperature responsive bar l3 will be positioned quite close to the associated device.

In the operation of the temperature control de- 1 vice, it will be understood that the fixed contacts 43 and 44 will be electrically connected to the cir cuits to be controlled, or will be connected in suitable controlling circuits for the circuits to be controlled. ,In operation, the bridgingcontacts 4| and 42 are moved by the bimetallic bar I3 in acordance with temperature changes. In one specific application, the bimetallic bar: I3 and the switch arm 39 are in their positions shown in Fig. 1 so as to close the contacts 44 as long as the temperature of the device whose'temperature is being controlled is below the predetermined maximum temperature for which'thedevice is set to operate by the adjusting screw l5. In the closed position of the thermostat, it will be observed that the bearing 40 at the left-hand end of the arm, as viewed in Fig. 1, bears upon the upper surface of the base of the U-shaped spring member 24, while the right-hand lug 3| limits the relative movement of the switch arm 30 away from the spring. It will also be observed that the comprcssion spring 35 exerts a force on the spring member 24 and on the switch arm so as to bias these members together, that is, so as to tend to remove the clearance between the switch arm and the base of the spring atthe right-hand side of the spring. The force of this spring 35, however, is overcome by the force of the U-spring 24 which forces the bimetallic bar I3 into the position shownin Fig. 1 when the temperature of the bar is below a predetermined value.

, As the temperature of the device increases, the distortion of the thermostat bar l3 tends to move its free end upwardly against the force of the spring 24, and upon the occurrence of the predetermined maximum temperature for which the device is set, the-thermostat bar l3 will overcome the force applied to it by the spring 24 and will move upwardly and rapidly accelerate to and through a neutral position to the opposite side thereof, whereby the bridging contact .42 opens the fixed contacts 44 and the bridging contact 4| closes the fixed co'nt-acts 43. .The contacts 44 are quickly opened by the snap action of the thermostat, while the contacts 43 will be quickly closed. 'The snap action is enhanced by the flex ble connection between the switch arm 30 a id'the spring 24. Thus, it will be observed that the initial relatively slow movement of the thermostat bar will be absorbed by the limited space between the switch arm 30 and the right-hand side of the base of the U-shaped spring 24, and that the bar l3 will be given opportunity to accelerate to a relatively high speed before the switch arm is engaged by the spring 24 to open the contacts 42 and to close the contacts 43.

The spring 24 will hold the switch contacts 43 closed until the temperature of the device is lowered to a predetermined minimum, whereupon the bar I3 will quickly move the switch arm 30 to break the contacts 43 and to make the contacts 44. When the contacts 43 are closed by the bridge 4i the right-hand bearing 40 of the switch arm 30 will bear upon the right-hand side of the U-shaped spring member 24, while the left-hand bearing will be removed from the ad jacent side of the U-shaped spring member 24 to provide a clearance space between these ends of the switch arm and the base of the spring similar to the clearance between the right sides of these members shown in Fig. 1. This clearance will be limited by the left hand lug 3|, and, as before, will permit the bar l3 to gain considerable velocity before the spring 24 engages the switch arm 30 to open the contacts 43 and to close the contacts 42.

In other words, when the bimetallic bar I3 is operated between its controlling positions, the switch arm'3il will be rotated on transverse axes passing through the bearings 40, the particular axis depending upon whether the bimetallic bar I3 is moving upwardly or downwardly, as viewed in Fig, 1; when it moves upwardly, the switch bar 30 rotates on the left-hand bearing 40, whereas when the bar I3 moves downwardly, it rotates on the right-hand bearing 40, and in each case, by reason of this rotation, the bimetallic bar is given an opportunity to acquire considerable velocity before the control arm 30 is actuated. In view of the fact that the pin 36 is located centrally of the spring 24, there is an equal amount of rocking of the arm 30 on both sides of the neutral position.

It will also be observed that the switch arm 30 I can rotate on these bearings on the longitudinal axis passing substantially through the center of the spring member 24, whereby the bar can accommodate itself to irregularities or inaccuracies of the contacts.

The loose connection between the switch arm 30 and the spring 24 has the further advantage that the switch contacts are caused to move into and out of engagement with a wiping action thereby preventing the accumulation of dirt or other deposits on either the movable or the stationary contacts. For example, when the bimetal bar I3 is moving upwardly, as viewed in Fig. 1, the U-spring 24 rotates in an upward direction about the pivot 25. This action of the spring 24 moves the switch arm 30 toward the left until the clearance between the spring and the switch arm at the right side has been absorbed when the spring will engage the arm to move it upwardly. This shiftingof the switch arm toward the left by the initial movement of the bimetal bar draws or wipes the bridging contact 42 across the fixed contacts 44. Similarly, when the bimetal bar moves downwardly, the bridging contact 4| is caused to wipe the fixed contacts 43. In either case, when the switch arm is rotating on the proper bearing 40, it rotates at the same time with reference to the upper pin head 3! on the bearings 38.

As pointed out previously, the temperature setting of the control device is adjusted by means of the rod l5, whereas the range between the maxi mum temperature at which the bimetallic thermostatic bar I3 moves to open the contacts 44 and to close the contacts 43 and the minimum temperature at which it is moved to open the contacts 43 and close the contacts 44 is effected by changing the position of the fixed bearing 23.

In the modified form of this invention shown in Fig. 3, only one set of fixed contacts is provided. As shown in this figure, one set of fixed contacts I is mounted upon an insulating supporting body II which in turn is supported in a casing 12, similar to the casing I0, II, I2 of Figs. 1 and 2. Cooperating with these contacts is a bridging contact I3 which is carried by a control arm 14. This arm is mounted on the base of a U-shaped spring I which, as shown, bears on the free end of a bimetallic thermostat bar I6. The arm I4, the spring I5 and the bar I6 all are arranged in substantially the same fashion as are the corresponding parts shown in Figs. 1 and 2, except that the bar I4 does not carry the second upper bridging contact, because the upper set of fixed contacts have not been used, and the control device in Fig. 3 operates in substantially the same manner as does the control device of Figs. 1 and 2. In Fig. 3, however, a suitable adjustable stop member 11 is arranged to engage the Uspring I5 when the thermostat bar I6 has operated the switch contact I3 to its open position, as shown in dotted lines in Fig. 3. This stop II, as shown, is in the form of a screw which is threaded in the end wall of the casing adjacent the spring I5. The stop 11 is held in its adjusted position by means of a lock nut I8.

While I have shown particular embodiments of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A temperature control device comprising an element arranged to change its position in response to changes in temperature, an elastic member operably associated with said element arranged to cause it to change its position quickly, a control member and connection means between said control member and said elastic member providing for movement of said control member with reference to said elastic member on each of a plurality of substantially parallel axes arranged in a preselected direction, and also on a third axis substantially perpendicular to said parallel axis, said connection means preventing substantial relative movement of said control member to said elastic member on axes arranged in any other than said three axes.

2. A temperature control device comprising a bimetallic thermostat bar arranged to move between a pair of controlling positions responsively to changes in temperature, a substantially U- shaped spring bearing on said bar so as to cause it to move quickly between said controlling positions, and a substantially rigid control arm mounted lengthwise on the base of said U-shaped spring movable by said spring between a pair of fixed members, bearings on said switch arm spaced longitudinally thereof so as to rest on the end portions of said base, said arm pivoting on said bearings to move in opposite directions away from said base on a pair of substantially parallel transverse axes when said arm engages said fixed members respectively, and said bearings providing for pivotal movement of said control arm on an axis extending through both of said bearings longitudinally of said base at substantially right angles to said pair of parallel axes, and resilient means between said arm and said base biasing said arm toward said base.

3. A temperature control device comprising a bimetallic thermostat bar arranged to move between a pair of controlling positions responsively to changes in temperature, a substantially U- shaped spring bearing on said bar so as to move said bar quickly between said controlling positions, the base of said spring moving in the plane of movement of said bar, a substantially rigid switch arm mounted lengthwise on the base of said U-shaped spring member so as to move in the plane of movement of said thermostat bar between a pair of controlling positions, switch contacts engaged by said switch arm in each 01 said positions, knife-edge bearings on said switch arm spaced longitudinally thereof so as to rest on the end portions of said base, a pair of lugs on said arm spaced longitudinally thereof between said spaced bearings, said lugs projecting through a pair of spaced apertures provided for them in said base, retaining means preventing the withdrawal of said lugs from said base, but providing for limited relative movement of said arm and said base, a pin passing through apertures provided for it in said arm and base substantially midway between the bearings on said arm, heads on the opposite ends of said pin, a compression spring interposed between the under side of said base and the head of the pin on that side and a pair of knife-edge bearings on the outer side of said switch arm on opposite sides of said pin bearing against the other head on said pin.

4. A. temperature control device comprising a bimetallic thermostat bar arranged to move between a pair of controlling positions responsively to changes in temperature, a substantially U- shaped spring bearing on said bar so as to move said bar quickly between said controlling positions, the base of said spring moving in the plane of movement of said bar, a substantially rigid switch arm mounted lengthwise on the base of said U-shaped spring member so as to move in the plane of movement of said thermostat bar between a pair of controlling positions, knifeedge bearings on said switch arm spaced longi- .tudinally thereof so as to rest on the end portions of said base, connection means between said switch arm and said base providing for limited movement of said arm on said bearings relative to said base,. a pin passing through apertures provided for it in said arm and base substantially mid-way between the bearings on said arm, heads on the opposite ends of said pin, a spring interposed between the under side of said base and the head of the pin on that side and a pair of knife-edge bearings on the outer side of said switch arm on opposite sides of said pin bearing against the other head on said pin.

WALLA CE J. ETTINGER. 

